The troubled blood testing company Theranos has announced another 155 layoffs, just months after cutting 340 staff in October. In total the company, which was once one of the country's most valuable tech startups, has cut about 70% of its staff in the last three months.

Theranos said about 220 employees will remain in the slimmed-down version of the company, which will focus on developing a new blood testing machine.

Today's move comes more than a year after the original vision for Theranos — to develop technology allowing consumers to get cheaper blood tests that require just a few drops of blood — began to unravel. A series of Wall Street Journal articles revealed the company's much-hyped technology frequently returned inaccurate results, and that it had quietly begun relying on commercially available testing machines.

Theranos was once considered a high-profile success story in Silicon Valley, with investors valuing the startup at $9 billion. The valuation made its founder, Elizabeth Holmes, the youngest self-made female billionaire, at least on paper. She has since been banned from operating a clinical lab by the Center for Medicare and Medicaid Services, which she is appealing.

The company had previously offered blood tests to the public through outlets at Walgreens stores in Arizona, and planned to roll them out nationwide. Walgreens was one of the company's many high profile investors, but it has since severed ties with the company. In November it filed a lawsuit against Theranos, saying the company "failed to meet the most basic quality standards."

As Theranos cuts down its staff, property developers are eyeing its Palo Alto headquarters. The building was recently sold to Kilroy Realty Corp, the San Francisco Business Times reported this week. The Los Angeles-based developer is a major real estate investor in the Bay Area.

Theranos rents its space in the building, which was previously owned by Stanford University's real estate division, which built it on the site of a former Wall Street Journal printing press.

Matthew Zeitlin is a business reporter for BuzzFeed News and is based in New York. Zeitlin reports on Wall Street and big banks.